Multiphase flow occurs when more or less separate phases of gases, liquids and/or solid particles flow simultaneously as a mixture. Multiphase flow may involve complex irregular interactions between the flowing phases inducing pressure drops, deposits, liquid accumulation and unstable flows. These phenomena may occur in a wide range of applications ranging from large scale industrial processes such as i.e. pharmaceutical industry, paper industry, food industry, metallurgical industry, to small scale applications such as i.e. cooling systems, combustion engines etc.
One particular area where understanding and managing multiphase flow is of vital importance is transportation of hydrocarbons in pipelines from the production sites to processing plants. Fluid flow in pipelines from oil- and gas fields typically involves simultaneous flow of water, oil, and gas, and may also contain entrained solids. The flow patterns may take many different regimes, such as slug flow, bubbly flow, stratified flow, annular flow, and/or churn flow.
The present development of oil- and gas extraction is towards more technically challenging areas such as the arctic and deep water and also in the marginal fields in harsh environments. It has thus become more important to understand and predict possible multiphase behaviour and complex fluid-related effects which may occur in the pipelines during design and operation of oil- and gas transportation lines. The basic objective for operators is optimized production under optimized safety-conditions, resulting in a need for controlling the flow velocities, pressure variations and fluid temperatures in the pipelines.
The irregular and complex behaviour of multiphase flow makes it necessary to use numerical simulations, often assisted by extensive experimentally determined flow parameters, to predict and/or to obtain an understanding of the multiphase behaviour and complex fluid-related effects that may be expected to occur in a specific pipeline.